"the principal article of faith of the great German reformer Martin Luther."
Martin Luther by Lucas the Elder. 1533
Public DomainMartin Luther by Lucas the Elder. 1533 - Credit: Wikimedia Commons

Martin Luther (10 November 1483 - 18 February 1546) was a German priest and professor of theology, renowned for initiating the Protestant Reformation in Europe.  His 'justification by faith' claimed that salvation was only to be obtained by God's grace through belief in Jesus Christ as the Messiah, and not through the penances and good works prescribed by the Church, whose practices he came to consider corrupt. 

He translated the Bible into German, making it available to many more people and eliminating the authority the Church derived from reading the text only in Latin.

Catherine Parr believed that the apparatus of Catholic services was both unnecessary and an obstacle to true belief and salvation. She attempted to convert Henry to her views.